Songs you know, whats the point of testing something you dont know regardless of it's dynamic range, bandwidth, bass response and so on, i could reccommend a thousand songs but if you dont know the song or what it sounds like on your gear you still wont know. Many years ago hi fi shops would play the familier hi fi test records of dire straits, fleetwood mac, rikki lee jones etc, etc and nearly all would sound good so you could start there but most dealers, if they are good ones encourage you to bring your own recordings.